Hybrid redundancy interface

ABSTRACT

The interface disclosed herein is capable of operating in the TMR/S (triple modular redundancy with sparing), the comparison, and the simplex modes. The interface controls the interconnection between m1 , . . . , mn identical sending modules and M1 , . . . , Mn identical receiving modules. To this end, there are provided 1, . . . , n control registers which comprise 1, . . . , n bits and an (n+1)th control register which comprises a single bit RS. The register bits are employed to provide n2 forcing functions for the outputs d1, . . . , dn of the sending modules which are represented by the following logical equation:   WHEREIN J IS THE BIT NUMBER, 1, . . . , N, I IS THE REGISTER NUMBER 1,..., N, THE SYMBOL N SIGNIFIES MODULO N AND V represents the OR function. The n2 forcing functions are respectively applied in sets of n viz., f1i, f2i, . . . , fni i 1,2, . . . , n to (1, . . . , n)th threshold function circuits, each of the latter circuits producing a &#39;&#39;&#39;&#39;1&#39;&#39;&#39;&#39; output when &gt; OR = 2 of the inputs thereto are &#39;&#39;&#39;&#39;1&#39;&#39;&#39;&#39;, the outputs of the (1, . . . , n)th threshold function circuits being applied to the M1, . . . , Mn)th receiving modules, respectively. From the register settings and the sending module outputs, there are generated pairs represented by the logical equation Cij (di V Rij V Rji V RS, djRijRji V Rs) for j i+1 (i 1, 3, 5, . . . , n-1) Cij (di V Rij V Rji, djRijRji) for j NOT = i+i WHEREIN THE IJ PAIR IN THE FIRST EQUATION CAN TAKE THE VALUES OF 13, 14, . . . , 1N, 24N, . . . , (N-2)N. From the pairs, (ij), there are generated register triggers having the following equations: A1 +/C12 Lambda M C13 M C14 Lambda M . . . Lambda M C1n A2 +/C21 Lambda M C23 Lambda M C24 Lambda M . . . Lambda M C2n An +/C1n Lambda M C2n Lambda M C3n Lambda M . . . Lambda M C(n 1)n WHEREIN THE SYMBOL Lambda M represents the morphic AND function called the RCCO in U.S. Pat. No. 3,559,167, the symbol + signifies the exclusive OR function on the pair of lines that are outputs of the morphic AND. The (A1, . . . ,An)th triggers are applied to the (1, . . . , n)th bits of the registers respectively, to switch the bits to the opposites of their initial binary states whereby, upon the generation of a register trigger Aj and the consequent switching of register bits R1j, . . . , Rnj to their opposite binary states, sending module mj is disconnected from operation. To operate the interface in the TMR/S mode, initially all of the bits of the (1, . . . , n)th registers are initially set to the 1 state and the bit of the (n+ 1)th register is set to the 0 state. To operate the interface in thE comparison mode, all the bits bearing the same numerical designation as the sending module which are to be compared in the registers bearing the same numerical designations as the sending modules which are to be compared are initially set to the 1 state with all of the other bits set to the 0 state. To operate in the simplex mode, all of the bits in the (1, . . . ,n)th registers except those bearing the same numerical designation as that borne by the register in which they are contained are set to the 0 state, the excepted bits being set to the 1 state. Also, in the simplex mode of operation, the bit of the n+1th register is set to the 1 state.

provide n forcing functions for the outputs d United States Patent 9] Carter et al. it

[ Dec. 18, 1973 HYBRID REDUNDANCY INTERFACE lnventors: -William C. Carter, Ridgefield,

Conn.; Aspi B. Wadia, Shrub Oak, NLY.

International Business Machines Corporation, Armonk, NY.

Filed: 1 June 20,1972 Appl. No.: 264,666

Assignee:

[56] References Cited 4/1972 Gunning et a1 235/153 AE 5/1972 Bouricius et al. 235/153 AE Primary Examiner charles E. Atkinson Attorney-Isidore Match et a1.

[ 5 7 ABSTRACT The interface disclosed herein is capable of operating in the TMR/S (triple modular redundancy with sparing), the comparison, and the simplex modes. The interface controls the interconnection between m m, identical sending modules and M M identical receiving modules. To this end, there are provided 1, n control registers which comprise l,

n bits and an (n+1 control register which comprises a single bit R The register bits are employed to of the sending modules which are represented by the following logicaleguationf fii i ii ii i|i+11 iii'l'n2i wherein j is the bit number, 1, n, i is the register number 1,,.., n, the symbol l in signifies modulo n and V represents the OR functio n. The n forcing functions are respectively applied in sets of n viz., f,i, f i, ,f,,ii= 1,2,. n to (l, n)" threshold function circuits, each of the latter circuits producing a *l" output when 2 cuits being applied to the M,,

2 of the inputs thereto are *l, the outputs of the (l, a) threshold function cir- M,.)" receiving modules, respectively. From the register settings and the sending module outputs, there are generated pairs represented by the logical equation 1 Cu 2 V RU V R]; V R5, d RUR forj (i=l,3,5,...,n-l) CU Ru V R forj 7 wherein the ij pair in the first equation can take the values'ofl3, 14,. ln,24,. .,2n,. .,(n-2)n. From the pairs, (ij), there are generated register triggers having the following equations:

14.1: =GB/CUIAM 2n M tln M AM (n-Un wherein the symbol A represents the morphic AN function called the RCCO in US. Pat. No. 3,559,167, 1

the symbol69signifies the exclusive OR function on the pair of lines that are outputs of the morphic AND. The (A ,A,,)" triggers are applied to the (l, n)"' bits of the registers respectively, to switch the bits to the opposites of their initial binary states whereby, upon the generation of a register trigger A,

and the consequent switching of register bits R R, to their opposite binary states, sending module m, is disconnected from operation.

To operate the interface in the TMR/S D are to be compared are initially set to the 1 state with all of the other bits set to the 0 state. To operate in the simplex mode, all of the bits in the (l, ,n Y"

registers except those bearing the same numerical designation as that borne by the register in which they are contained are set to the 0 state, the excepted bits being set to the 1 state. Also, in the simplex mode of operation, the bit of the n+l" registeris set to the 1 state.

7 Claims, 7 Drawing Figures PAIENTEBDEIIIBiSYS o?owo ov 23328205: Om. .ZO0 2mkm m o owo o ofowowor f o" 5 NE mE v2 mo PATENIED an: 1 a 1915 sum 5 BF 6 g allrrllL 5 2L PMENIED M818 I973 sum 5 OF 5 Edi HYBRIDREDUNDANCY INTERFACE BACKGROUND or THE INVENTION This invention relates to high reliability computer systems. More particularly, it relates to a novel hybrid redundancy interface for such system.

A known technique for achieving high reliability in a computer system is to partition the system into serially connected modules, replace each of the modules by a set of n identical copies, and then provide means for in terconnecting these sets of copies whereby the system operates in the TMR/S (triple modular redundancywith-sparing) mode. In this technique, there are generally employed three identical input buses ,to fan out to all of the n copies of a module. In this type of arrangement, only three modules (desirably, the correctly operating ones), are connected to three output buses.

The known technique described hereinabove and ,the organization for its implementation is deficient in that asingle bus failure cripples the total system.

Accordingly, it is an important object of this invention to provide a system wherein a bus failure does not deleteriously affect operation.

It is anotherzobject to provide a simple interface which controls the interconnections between identical copies of one module with n identicalcopies of another module, both ofwhich appear as serially conn ectedin the operation of a simplexsystem.

It is. a further object to provide an interface as set forth in thepreceding object which provides interconnection forthe interface to operate in-the'TMR/S, comparison and simplexmo'desu t r It is still another object to provide an interface wherein everyfailure in the ,interfaceappears either as a a failure of one ofthemodules it feeds intoand wherein the ,effectof the failure is maskedby-theswitching of the same module or the automatic correction of the failure.

SUMMARY OF THE INVENTION In accordance with the invention, there is provided an interface for controlling the interconnections between m m identical sending modules and M, ,M,, identical receivingmodules. The invention comprises 1, n control registers, each ofthesereg- 'isters comprising n bits and an (n+1 control register comprising a single bit R Means are included for setting the bits of the registers to chosen initial ,statesto enable the interface to operate in theTMR/S, (triple modular. redundancy with sparing), comparison and simplex modes of operation. The sending modules provide d ,d outputs respectively. Inresponse tothe latter outputs, means are included for providing n forcingfunctions, each of the forcingfunctions being a circuit represented by the logicalequation binary t s. The outputs of the sets of n forcingfunctions f,i,f i ,f,,i i 1 n are applied to the mg more, particular :descriptionof preferred embodition andA (l n)"' threshold circuits, respectively. The outputs of the (l n)? threshold circuits-are applied to (M M,,)"' receiving modules respectively. There are also included means for generating pairs which are representedby the following logical equationf Cu i V V V sfljRu jr V s) wherein j =i+l and i takes on the, value 1,3,5 n-l and u i V u ii: J-RU JJ I wherein C is the-self-testing pair and the ij pair takes oneof the values of 13, 14 r In, 24, 2n, ,;l(n2)n. Means are provided for generating register triggersntilizing the abovementioned self-testing pairs, the triggers being represented by the following equations: I I

- AM zn Au B/ 1 MC2n M 3n M M (nltn wherein the symbolEBsignifies the exclusive OR function, the symbol A represents the rnorphic AND func- Qf, A are the register triggers. Means are irieluded for applying the (A, ,A,,)".- t rig gers to the (l ri) bits ofthe l l n)" registers respectively to switch the bits to theflopposites of their .initialbinaryflstates whereby, upon the generation of a register trigger A and the conse q uent sjwitchin g of register bits R R,,,- to the opposite binary states, sending module m, is disconnected.

The inventive interface is capable of operating in the TM /s (tripl modul lxd q yw p ng). the comparison,and simplex modes ln the TMR/S mode, the bitsof registers l ntare initially set to the binaryst e and the bit of the (h-|- l)"' register is set to the ,O binary state. In the comparison rnode, all of the ,bits in the registers are initially set to the 0 binary state except the bits having thesame numerical designations as then umer ical designations of the sending, modules to be comparedin the registers having the latter send- .ingi module designations,,these bits being set to the l ,statef, In the simplex mode, the bit in the (n+1 ,register is set to the l binary state. All of the bits in the i (l .,n)"' registers areset to the state, except that bit in a registerbearing the same numerical designation .as the register designation. In the simplex ,mode of ,operatiomsending modules m, m are respec' tively connected through the 1 interface to receiving modules M, ,M.,, I I t I Theforegoing and other objects, features and,advan tages of the invention willlbe apparent from the following drawings.

, BRIEF DESCRIPTION OF THE DRAWINGS I -ln the drawings,

FIGS. lA to 1F, taken together asinFlG. l constitu te a depiction of a preferred embodiment con DESCRIPTION OF A PREFERRED EMBODIMENT ,structed in accordancewith the principles ofthe inventlon.

pln the irivention described hereinbelow, there is provided an interface between two sets of modules, viz., {m,, m ,m }and{M,, M M,,}wherein m, and M,-, wherein i= 1, n, are identical replicas of m and M respectively. The interface provides interconnection between the two sets of identical replicas whereby a system can function in the following three modes:

MODE 1 TMR/S (Triple Modular Redundancy With Sparing) In this case, the system has to operate in the TMR mode. Upon the detection of a module failure, the failed module has to be switched off and one of its spare copies switched in. The switching off and switching in continues until the occurrence of (n-2 module failure within a set of 11 identical copies at which stage, automatic switching into the comparison mode has to occur. The next failure exhausts all correction and detection capability and operation in this mode ceases. Operation, unchecked, can be continued subject to external state setting determined by software.

MODE 2 Comparison In this mode, the system starts off with modules m, and m respectively, connected to modules M, and M handling one process, modules m and m connected to modules M and M handling another process, etc., whereby the system handles [n/2] processes in parallel, each process being in a duplication and comparison mode. Upon the detection of a failure, the process in which the failure occurred reverts to diagnostic procedures. The mode ends when the last process is in a diag-' nostic procedure because of an [rt/2] solid failure.

MODE 3 Parallel Processing In this mode, the system operates with module m, connected to module M, wherein i l, n. Consequently, there is enabled the running of n processes in parallel. MODE 4 Simplex Mode The interface also provides connections for the n copies of a simplex module whereby operation of the system can continue until all n of one set of modules have failed using software error detection, diagnosis and status setting.

MODE 5 Mixed Mode I Any combination of the TMR/S, TMR and comparison modes may be run, subject to the limitations of the number of modules. For example, with 6 modules, a possible set of combinations is l TMR/S (4 modules), and 1 comparison (2 modules). Clearly, other combinations are possible and obvious.

Reference is now made to FIGS. 1A to 1F taken together as in FIG. 1 which constitute a depiction of a preferred embodiment of the interface constructed according to the invention. In these FIGS., there is shown the examples wherein there are utilized four sending modules m, m and four receiving modules M, M The interface is controlled by the contents of four registers R,, R R and R Each of these registers has a length of4 bits. In addition, there is shown a 1 bit register R the operation of which will be further detailed hereinbelow. Initiation of the operation of the interface in a particular mode is effected by the system control stage 10 which effects the initial settings of the registers, such system control stage suitably being a component of a computer and which may be programmed for its setting function. Thereafter, if the system is operating in the TMR/S or Comparison mode, automatic required switching is achieved. In the further description of FIGS. 1A- IF, the modules m, m numerically. designated by the numbers l2, l4, l6, and 18, are termed sending modules and the modules M, M designated by the numerals 20, 22, 24 and 26, are suitably termed receiving modules.

In the operation of the interface, each receiving module M,- wherein i l4, receives as input the result of a threshold voting on the output of all ofthesending modules m, m,. The input to each threshold voter is controlled by the forcing and gating function f,-,. In the FIGS., there are shown four forcing functions groups f,

to f,

Considering the operation of forcing function I-",. it is seen that there are provided therefor, the AND circuits 28, 30, 32, 3'4, 36, 38, 40 and 42, and the OR circuits 44, 46, 48 and 50. The inputs to AND circuit 28 are the output line 101, i.e., output d, of sending module m, and the set output line 117 of flip-flop R,, of register R,. The inputs to AND circuit 30 are the reset output line 118 of flip-flop R,,, the reset output line 116 of flip-flop R of register R, and the reset output line 114 of flip-flop of R, of register R,. The output lines of AND circuits 28 and 30 are applied to an OR circuit 44. Similarly, to AND circuit 32, there is applied the line 102, i.e., output d, from sending module m To AND circuit 36 there is applied the line 103, i.e., output (1 from sending module m,, and to AND circuit 40, there is applied the line 104, i.e., output (1,, from sending module m.,. The remaining inputs to AND circuits 32, 34, 36, 38, 40 and 42 are the particular flip-flop output lines as shown in FIGS. The outputs of AND circuits 32 and 34 are applied to the OR circuit 46. The outputs of AND circuits 36 and 38 are applied to the OR circuit 48 and the outputs of AND circuits 40 and 42 are applied to the OR circuit 50. The bits in each of registers R, R, and the equations of the forcing functions f,f are as set forth immediately hereinbelow.

Four 4-bit registers 14 R, R,, Register R, 24 23 2 Register R 34 33 32 Register R 44 43 R42 4 Register R Equation of Forcing Functions f1 f11 1 11 V luKmEur f21 2 m V 512513514 fin a m V 11351-1511 f41 4 l4 V 14 11 12 f2 fl. 111:2. v 511E25 f22 2 22 V 822523524 fiiz a 2s V 523524551 f-tz 4 24 V 24 z1 22 f13 I BI V l gzgaa f23 z sz V lsfizmfiaq fizz a sa V 533534531 1 43 4 a4 V aa m az fm 1 41 V 4152543 f24 2 42 V 42543544 fin a 'aa V 43 44 41 f 4 44 V u 42 wherein the symbol V represents the OR function.

There are provided four voting circuits 52 54, 56 and 58 whose inputs are controlled by their associated forcing functions, each of these circuitsbeing a Z 2 circuit threshold function which is a circuit which pro duces a binary 1" output if 2 of its i nputs are a binary l. Thus, for example, threshold voting circuit 52 comprises the AND circuits 60, 62, 64, 66, 68 and 70,the outputs of the latter AND circuits being applied to an OR circuit72, the output of OR circuit 72 being applied to receiving module M The logical equations for the threshold voting circuit 52, 54, 56 and 58 are as follows: i

Threshold Circuit 52 Threshold Circuit 56 no; was, fnfim miss ans mans Threshold Circuit 58 m ina mm ar an. M 1

The outputs of threshold voting circuits 54,56 and 58 are appliedto receiving modules M M and M re spectively.

lt is'noted that the various output lines of the flip-flop of registers R, R and lines 101, 102,; l03', and 1:04,

i.e., outputs d d d anddg are appliedto A'NDand OR No. 3,559,167. lt functions to reduce several'pairs of lines to asingle pair of lines which take on the values (0,1 or (1,0). An RCCO circuit may also be termed a morphic AN D circuit,

The-outputs of RCCO circuits 70, 7,2, 74and76 are respectively applied to exclusive OR circuits 71, 73, 75 and 77 to produce the triggers A A A and A lfor registers R}, R R and R The triggers areapplied as reset inputsto the flip-flops of the registers.

The equationsfor providing the A A triggers are as follows. In these equations, the symbol signifies exclusive OR; and the symbol A signifies morphic AND.

The operation ofthe circuit shown in FIG. 1 is now described forthe variousmodes of operation set forth hereinabove.

IJTMRIS Mode In this mode, initially allof registers R R R and l R, are in the 1111 state and the flip-flop constituting register R is set to the 0 state, these states having been As long as no errors occur during operation, all C s will be and, consequently, all A s are equal to 0,

a. First Error l I. Letit be assumed that it is sending module m which produces the first error. In this situation, pairs C C and C take on the values and C C and C remain at At this point trigger Aygoes to l and triggers A A and Ai, remain at(). Consequently, trigger A resets the rightmostbitof eachregister R R whereby their slate's' all become 1 l 10; Consequently, sending module m, is disconnecteda nddata from sending modules m i m and m, are thresholdvoted andsent to all receiving modules M M Mg and M The TMR operation continues. At this juncture, the C pairs areas follows:

23 zi s) 2 2, 4) 34 =1 (dado Trigger A takes on the value of l and triggers A,,

A}, and A remain atO. With the value of l for A the secondrightmost bits of, registers R, R are set toO-and the register states go to llOl. Sending module m is thereby disconnected, Data from sendingmodules m3, m and m are threshold voted and sent to all receiving modules M, M TMR operation continues. The C pairs values are now as follows:

C13 u s) C14 u -a) Trigger A stays at l and triggers A,, A and A, are at 3. Let it be assumed that sending module m produces the first error. In this case, trigger A goes to l. TriggersA A and A, 0. Registers R, R to the 1011 stage. Sending module m is thereby disconnected. Data from sending modules m,, m and m, are threshold voted and are sent to all receiving modules M, M TMR operation continues.

4. Let it be assumed that it is sending module m, that produces the first error. In this situation, trigger A, goes to 1. Triggers A,, A and A 0. All registers R, R go to the 01 11 state. Thereby,sending module m is disconnected. Data from sending module m m and m are threshold voted and sent to all receiving modules M, M.,.'TMR operation continues.

b. Second error This case is explained with the example of m being the first sending module in error followed by the erroneous state of sending module m Prior to sending module m s becoming erroneous, the condition which was obtained by the erroneous state of sending module m was 1, 1 112 and A1=A A4= O All registers R, R are in the 1101 state. Sending module m was disconnected. I

Now, theoccurrence of the error in sending module m causes pairs C C,,

and pair C remains at If, now, either of sending modules m, or m, becomes erroneous, C goes to 8 0, 0 l 1} Consequently, A, A A A 1 whereby all of registers R, R go to the 0000 state and operation halts. It halts because there is no way of determining which of sending modules m, or m was in error. Therefore, both of the latter modules are disconnected. Further computation depends on software action.

COMPARISON MODE To enable operation in the comparison mode, the following settings have to be put into registers R, R Register R remains in the 0 state for all of these settings. These settings are effected by system control Thus, for example, if it is desired to have two processes running in the comparison mode such as for example sending modules m, and m, in one process, and sending m and m, in the other process, then the settings in the registers will be as follows:

In the switching operation whereby sending module m, and m and sending modules m and m are being respectively compared, the pairs C,,- take the following values: 7

12 C13 u s) C14: 23 C24: 2 4) 34 A, 3 1%) and 2 A. (112%.)

I SIMPLEX MODE In this mode, the bit constituting register R is set to The settings in registers R, R, and the resulting respective sending to receiving module connections are as follows:

Setting in Registers Resulting Sending To RI. 4 Receiving Module Connections R,=O00l m,toM, R,=00I0 m, to M R =OIOO m toM R,= 1000 m to M,

Because register R is at l, triggers A, A, are all j and the value of the C pairs in different situations encountered in the several modes of operation of the invention. The check marks, under C,- ,-s mean that the two lines have the values d,-,d,- and are not forced. to

M and the forcing functions and threshold functions automatically perform TMR (triple modular redundancy).

lfj j are used with i i to determine bits in registers R R, (e.g., R3 ,R R R are l, the other bits then the forcing functions and threshold funcconstant values. The tabulations are based upon the tions automatically perform comparison of m and m embodiment shown in FIG. 1. 2 with outputs M and M TMR/S MODE OF OPERATION Register R1 Register R2 Register R: Register R1 Register 14 13 12 11 21 R23 R22 R21 11 11 32 11 44 11 42 R11 R 11 C13 C11 C23 C24 C31 1 .1 1 1 1 1 4 1 1 1 1 1 1 1 1 1 1 o 1 1 1 1 1 1 l 1 0 1 1 1 0 1 1 1 0 1 I 1 1 O 0 1O 10 l 1 1 1 1 O 1 1 1 0 1 1 1 O 1 1 1 O 1 0 10 l 1 1O 10 l 1 0 1 1 1 0 I 1 1 1 O .1 1 l 0 1 l O 10 1 10 V 1O 0 1 1 1 O 1 1 l 0 i 1 1 1 0 1 1 1 O l/ 1 1O 1 1O 10 wherein the line designations for the register settings and the values of the Cii pairs correspond.

Simplex mode of operation m1 130 M1 m: to M1 mg to M1 1114 120 M1 1 (9.) Com arison of two input modules feeding into all output modnles This situation arises for example when the, comparison moderis entered into from the TMB mode). In this case, all registers containexaetly the same two bits on. The checks show the input modules being compared.

(or more) bits are chosen in 4 (or more) registers.

The combinations are obvious to one skilled in the art, and the following example shows an illustrative case.

Operationinthe mixed mode can be better explained by the properties of an interface that connects 6 input modules to 6 output modules. Here, there are required 6 registers R R R R R and R each of6 bit length anda one-bit register R The table shows the contents Register R4 Register R1 Register R; Register Rs Register R14 R13 R12 R11 R24 R23 R22 R21 R31 R21 R12 R11 R44 R41 R42 R41 R5 C12 C11. C23 C23 C21 C114 0 0 1 1 o 0 1 1 0 0 1 1 0 0 0 1 0 10 10 10 1o 10 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 10 v 10 1o 10 10 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 0 10 10 10 10 10 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 10 10 10 10 10 1 0 1 0: 1 0 1 0 1 0 1 0 1 0 1 0 0 10 10 10 10 y 10 1 1 0 0 1 1 0 0 1 I 1 0 0 1 1 0, 0 0 10 10 10 10 10 wherein the numerical line designations for the register settingsand the values of the Cn pairs correspond.

MIXED MODE of the control register in order to operate injthe TMR/S m r's n modes. 1 Let the registers be oflengthn in order to achieve in.- iii CO pa I 0 terconnections between n sending and n receiving ma- 1 R R3 R4 1 Connection chines. Let the bits mR be denoted as 001111 001111 001 1| 001111 m ,m,.m;,m

. h zMe R, R, R-, R R, R, n l I i 11 0000 110000 0 m,,m, M,,M,, Bit R in register R, when equal to l connects sending 1 module m, to receiving. module M; through the thresh-. old voter. lfR is equal to 0, then m,- is not connected While the invention has been particularly shown and to M,. 1 Ifj j j are used to determine bits in registerschosen y l9 29 3 8-, 1 1, 1 1 1 1 1 5 81 1 1 1 t R m j are all 1 and the other bits in the reg sters described with reference to a preferred embodiment thereof, it willbe understood by those skilled in the art that the foregoing and other changes in form and details may be made thereinwithout departing from the i are zero)\the n m m m are connected to M M spirit and scope of the invention.

TMR/S is performed with automatic switching if 4 (b) Comparison of two inputs feeding into two output modules. The last column shows the module connections. e.g., mi,;- Mr, means mi and m,- are compared and connected to Mr and M Register R4 Register R Register R1 Register R2 R24 R23 22 R21 024 Cal mm Mm R34 am R32 R31 R44 4: R42 R41 mu L'Ii i 14 R12 R12 Rn HOD MOO

OOH

Wherein the numerical designations for the register settings and the (Gij) values correspond.

In this case where module m1 is erroneous, we can operate as follows:

Register R Register R4 Register Ra Register R2 Cu 023 C24 025 m m Rn Connection Rat l a-4M:.4 Comparison. 10 mz.3#Mz. DO. 10 mz.4 M2.4 DO

COO

COG

GHQ

OOH

OOQ

'ooo

COO

wherein the numerical designations of lines correspond for the registers and the Cr; pairs.

between 1 M identical receiving modules comprising:

What is claimed is:

I. An interface for controlling the interconnections between m, m,, identical sending modules and M, M identical receiving modules comprising:

1 ,n control registers, each of said registers comprising n bits, wherein R is a register bit;

means for setting each of said bits to initial binary states;

d d,, outputs from said sending modules. re-

spectively;

means for providing n forcing functions, each of said functions being a circuit represented by the following logical equation:

fii i ii i i|i+1I ims-2h,

wherein j is the bit number of a register and takes the value of 1 n, i is the register number and takes the value 1 n, the symbol signifies modulo n and the symbol V represents the OR function;

1 n threshold function circuits which respectively produce a l output when 2 2 inputs thereto are l means for applying said n forcing functions in sets of n to said (1 n)"' threshold circuits respectively; and

means for applying the outputs of said (l n)"' threshold circuits to said (M M,,)"' receiving modules, respectively. wherein C,-,- is a self-testing pair and the ij pair takes the values of 12, 13, 14 ln,2,3,24,...,2n,...,(nl)n;,

means for generating register triggers which are represented by the following equations:

n ln M 2n M 3n M M (nl), n the symbol A represents the morphic AND function, wherein the symbol@ signifies the exclusive OR function on the two outputs of the A and A t A are said register triggers; and

means for applying said (A A,,)"' triggers to the (l n)" bits of said registers respectively to switch said bits to the opposites of their initial binary states whereby, upon the generation of a register trigger A,- and the consequent switching of the register bits R R to said opposite binary states, sending module m,- is disconnected.

2. An interface for controlling the interconnections m identical sending modules and M,

1 n control registers, each of said registers comprising n bits, wherein R, is a register bit;

means for setting each of said bits to initial binary states; 7

d, d,, outputs from said sending modules, re-

spectively;

means for providing n forcing functions, each of said functions being a circuit represented by the following logical equation:

t n and the symbol V represents the OR function,

tively produce a thereto are 1;

means for applying said n forcing functions in sets of n threshold function circuits which respec- 1 output when 2 2 inputs n to said (1 n)"' threshold circuits respectively; means for applying the outputs of said (1 n)"' threshold circuits to said (M modules, respectively;

means for generating pairs which are represented by the following logical equation:

o i V u V jia j ij J'i) 3. An interface for controlling the interconnections between m m identical sending modules and M M, identical receiving modules comprising:

1 n control registers, each of said registers comprising rz bits, wherein R,-,- is a register bit;

an (n+1 control register comprising a single bit R means for initially setting each of said bits to initial binary states;

d d outputs from said sending modules, re-

spectively;

means for providing n forcing functions, each of said forcing functions being a circuit represented by the following logical equation:

. M,,)"' receiving fu i wherein j is the bit number of a bit in control register 1, n, and takes the value of l n, i is the control register number and takes the value of l n, the symbol l ln signifies modulo n and the symbol V represents the OR function;

1 n threshold circuits which respectively produce a 1 output when 2 2 inputs thereto are u 1 n; means for applying said n forcing functions in sets of n to said (1 .i n)" threshold circuits respectively; means for applying the outputs of said (I n)"' threshold circuits to said (M M the receiving modules respectively; means for generating self-testing pairs which are represented by the following logical equation: a V o V F1: V s j ij ji V 5) andi= 1,3,5 l and u V b V n J U J'I) wherein C is said pair and the ij pair takes one of the valuesofl3,l4,...,ln,24,...,2n,...,(n-2)n; means for generating register triggers which are represented by the following equations: A =B/C A C, A C A A C A g zi u zs u za u u zu wherein the symbol 6B signifies the exclusive OR function, on the two outputs of the A and A said register triggers; and

means for applying said (A A,,)" triggers to the (l n)",' bits of said (1 ,n)"' registers, respectively to switch said bits to the opposites of their initial binary states whereby upon the generation of a register trigger A,- and the consequent switching of register bits R R to said opposite binary states, sending module m, disconnected.

4. An interface as defined in claim 3 wherein said interface is rendered operative in the TMR/S (triple modular redundancy with sparing) mode of operation in response to the setting, by said initial states setting means of all of the bits in said It registers to said I state and the setting of the bit of said (n+1 register to said 0 state, the occurrence of (n-2) failures in said sending modules causing said interface to operate in the comparison mode of operation.

5. An interface as defined in claim 3 wherein said interface is rendered operative in the comparison mode of operation, i.e., thecomparing ofsending modules m, and m of said 1 n sending modules connected to M,, and M in response to the setting by said initial states setting means of bits h and k of said registers R,, and R to said 1 state and the remaining bits of said (I n)"' registers to said 0 state, and the setting ofthe bit in said (n+1 register to the 0 state.

6. An interface as defined in claim 3 wherein said interface is rendered operative in the simplex mode of operation by the setting to the 1 state of the respective bit in each of(l n)"' registers having the number of its register, the setting of all of the other bits of said (1 n)" registers to the 0 state, and bythe setting of said (n+1 register to the I state.

7. An interface as defined in claim 3 wherein said interface is operative in the mixed mode of operation, wherein said mixed mode takes the following form;

said n sending modules are partitioned into sets of pg groups of q modules wherein pg is an arbitrarily chosen integer denoting the quantity of groups with q modules operative, said value of pg being chosen to satisfy the following equation:

wherein pq can take the value of 0, whereby there are provided p groups of modules being operated in the comparison mode, p groups of modules being operated in the type modular redundancy mode, and for any value of q 24, pq groups of modules being operated in the triple modular redundancy mode with q-3 spares, wherein the values of pqare determined by the above equation, said n registers being set as follows by said bits setting means;

a q quantity of bits in each of said registers associated with each pq group of modules, at identical bit positions in said last-named registers and set to l, the sets of bits for each of said pq group associated registers being disjoint relative to each other, said R bit being initially set to O. 

1. An interface for controlling the interconnections between m1 , . . . , mn identical sending modules and M1 , . . . , Mn identical receiving modules comprising: 1 , . . . , n control registers, each of said registers comprising n bits, wherein Rij is a register bit; means for setting each of said bits to initial binary states; d1 , . . . , dn outputs from said sending modules, respectively; means for providing n2 forcing functions, each of said functions being a circuit represented by the following logical equation:
 2. An interface for controlling the interconneCtions between m1 , . . . , mn identical sending modules and M1 , . . . , Mn identical receiving modules comprising: 1 , . . . , n control registers, each of said registers comprising n bits, wherein Rin is a register bit; means for setting each of said bits to initial binary states; d1 , . . . , dn outputs from said sending modules, respectively; means for providing n2 forcing functions, each of said functions being a circuit represented by the following logical equation:
 3. An interface for controlling the interconnections between m1 , . . . , mn identical sending modules and M1 , . . . , Mn identical receiving modules comprising: 1 , . . . , n control registers, each of said registers comprising n bits, wherein Rij is a register bit; an (n+1)th control register comprising a single bit RS, means for initially setting each of said bits to initial binary states; d1 , . . . , dn outputs from said sending modules, respectively; means for providing n2 forcing functions, each of said forcing functions being a circuit represented by the following logical equation:
 4. An interface as defined in claim 3 wherein said interface is rendered operative in the TMR/S (triple modular redundancy with sparing) mode of operation in response to the setting, by said initial states setting means of all of the bits in said n registers to said 1 state and the setting of the bit of said (n+1)th register to said 0 state, the occurrence of (n-2) failures in said sending modules causing said interface to operate in the comparison mode of operation.
 5. An interface as defined in claim 3 wherein said interface is rendered operative in the comparison mode of operation, i.e., the comparing of sending modules mh and mk of said 1 , . . . , n sending modules connected to Mh and Mk in response to the setting by said initial states setting means of bits h and k of said registers Rh and Rks to said 1 state and the remaining bits of said (1 , . . . , n)th registers to said 0 state, and the setting of the bit in said (n+1)th register to the 0 state.
 6. An interface as defined in claim 3 wherein said interface is rendered operative in the simplex mode of operation by the setting to the 1 state of the respective bit in each of (1 , . . . , n)th registers having the number of its register, the setting of all of the other bits of said (1 , . . . , n)th registers to the 0 state, and by the setting of said (n+1)th register to the 1 state.
 7. An interface as defined in claim 3 wherein said interface is operative in the mixed mode of operation, wherein said mixed mode takes the following form: said n sending modules are partitioned into sets of pg groups of q modules wherein pg is an arbitrarily chosen integer denoting the quantity of groups with q modules operative, said value of pg being chosen to satisfy the following equation: 